Sulfamethoxazole and Its Metabolite Nitroso Sulfamethoxazole Stimulate Dendritic Cell Costimulatory Signaling

Abstract

Different signals in addition to the antigenic signal are required to initiate an immunological reaction. In the context of sulfamethoxazole allergy, the Ag is thought to be derived from its toxic nitroso metabolite, but little is known about the costimulatory signals, including those associated with dendritic cell maturation. In this study, we demonstrate increased CD40 expression, but not CD80, CD83, or CD86, with dendritic cell surfaces exposed to sulfamethoxazole (250–500 μM) and the protein-reactive metabolite nitroso sulfamethoxazole (1–10 μM). Increased CD40 expression was not associated with apoptosis or necrosis, or glutathione depletion. Covalently modified intracellular proteins were detected when sulfamethoxazole was incubated with dendritic cells. Importantly, the enzyme inhibitor 1-aminobenzotriazole prevented the increase in CD40 expression with sulfamethoxazole, but not with nitroso sulfamethoxazole or LPS. The enzymes CYP2C9, CYP2C8, and myeloperoxidase catalyzed the conversion of sulfamethoxazole to sulfamethoxazole hydroxylamine. Myeloperoxidase was expressed at high levels in dendritic cells. Nitroso sulfamethoxazole immunogenicity was inhibited in mice with a blocking anti-CD40L Ab. In addition, when a primary nitroso sulfamethoxazole-specific T cell response using drug-naive human cells was generated, the magnitude of the response was enhanced when cultures were exposed to a stimulatory anti-CD40 Ab. Finally, increased CD40 expression was 5-fold higher on nitroso sulfamethoxazole-treated dendritic cells from an HIV-positive allergic patient compared with volunteers. These data provide evidence of a link between localized metabolism, dendritic cell activation, and drug immunogenicity.

Drug Antigenicity, Immunogenicity, and Costimulatory Signaling: Evidence for Formation of a Functional Antigen through Immune Cell Metabolism

“…DCs express multiple drug-metabolizing enzymes (16,(19)(20)(21)(22) that can generate drugderived protein adducts in increasing amounts when exposed to danger signals (22). Furthermore, SMX-mediated DC signaling was shown to be dependent on intracellular metabolism and proteinadduct formation (16). One pathway for DC activation is through exposure to products derived from dying cells (e.g., ATP, heat shock proteins, HMGB1, urate phosphatidyl serine).…”

“…Drugs, including abacavir, amoxicillin, and SMX, were shown to partially stimulate human DC costimulatory signaling (16)(17)(18), which could potentially drive pathogenic immune responses in hypersensitive patients. DCs express multiple drug-metabolizing enzymes (16,(19)(20)(21)(22) that can generate drugderived protein adducts in increasing amounts when exposed to danger signals (22). Furthermore, SMX-mediated DC signaling was shown to be dependent on intracellular metabolism and proteinadduct formation (16).…”

Adduct Formation and Context Factors in Drug Hypersensitivity: Insight from Proteomic Studies

“…However, there are fewer studies exploring nature of the intracellular adducted proteins. In a study by Sanderson et al, binding of nitroso-sulfamethoxazole to the surface of dendritic cells as well as intracellular adducts of both sulfamethoxazole and nitrososulfamethoxazole were detected using immunological detection with an antibody against the drug [71]. More recently, the irreversible binding of nitroso-sulfamethoxazole and sulfametoxasole to APC has been reported and these cells were able to activate nitroso-sulfamethoxazole-specific T-cells.…”

Severe Cutaneous Adverse Reactions

“…The drug may also bind to toll-like receptors resulting in the expression of costimulatory molecules by dendritic cells. For drugs such as cotrimoxazole, lamotrigine, and carbamazepine, the p-i concept may not be the sole mechanism involved; metabolites may also play a role through haptenization [47].…”